1. Field of the Invention
The present invention relates to a thermally melted transfer recording medium, and more particularly to a thermal transfer recording medium producing high-resolution and solvent-resistant images.
2. Discussion of the Background
The thermally melted transfer recording medium is required to produce high-resolution images. Further, the produced images are required not to be erased with organic solvents such as ethanol, depending on the use environment.
In order to obtain good transferability, a method using a specific polyester resin as a thermally melted binder is disclosed. Japanese Laid-Open Patent Publication No. 63-51182 discloses a method using a polyester resin having a hydroxyl value of from 18 to 260. However, a thermal transfer recording medium produced by this method has good transferability, but durability of the resultant images, such as solvent resistance, is not satisfactory.
In addition, Japanese Laid-Open Patent Publication No. 2001-171233 discloses a method using a polyester having a specified solvent solubility. Japanese Laid-Open Patent Publication No. 10-129122discloses a method using a resin having a specified solubility and a parameter, and including acid-modified polyethylene into an ink. However, any of these methods do not produce a thermal transfer recording medium producing high-resolution and solvent-resistant images. Particularly, in a hedge-type thermal head printer, since a distance from a heating element to a point where a thermal transfer recording medium and a receiving material separate from each other is extremely short, and a printing speed is high, a time from application of energy to the separation is short. Therefore, an ink is not sufficiently fixed on the receiving material and it is difficult to produce images having good solvent resistance. A thermal transfer recording medium producing high-resolution and solvent-resistant images, which can be used in such a hedge-type thermal head printer is not available.
Because of these reasons, a need exists for a thermal transfer recording medium producing high-resolution and solvent-resistant images.
Accordingly, an object of the present invention is to provide a thermal transfer recording medium producing high-resolution and solvent-resistant images.
Briefly this object and other objects of the present invention as hereinafter will become more readily apparent can be attained by a thermal transfer recording medium including at least a substrate; a separation layer located overlying the substrate; and an ink layer located overlying the separation layer, wherein the separation layer includes at least a wax including a polyethylene wax, and wherein the ink layer includes at least a thermoplastic saturated polyester resin having a hydroxyl value of from 20 to 60 mgKOH/g; and an oxidized polyethylene having an acid value not greater than 5 mgKOH/g.
The polyethylene wax preferably has a melting point of from 100 to 120xc2x0 C. and a penetration less than 2 dmm at 25xc2x0 C.; the separation layer preferably further includes an ethylene-vinyl acetate copolymer resin and a carnauba wax and/or a candelilla wax; and the thermoplastic saturated polyester resin is preferably a reaction product of a dicarboxylic acid compound with a glycol compound, wherein the dicarboxylic acid compound includes at least an aromatic dicarboxylic acid.